In a small sauté pan, over medium high heat add the olive oil and the diced onions and shallots. Stirring often until the onions are translucent. Set aside to cool while you assemble the remaining ingredients
Put 4 slices into my food processor and pulse until they are fine crumbs. (Other options below)
In a large mixing bowl place the beef, pork, and veal. Add the bread crumbs, cooled onions, milk, eggs, herbs, salt and pepper. Mix with your hands until well combined.
You can make one big loaf or divide it into three small loaf pans like I did. This will be dinner for us for three nights and lunch for me for 3 days.
Top the meatloaf with the mushroom and onion sauce. I divided it up between the three loaves.
Bake @ 375° for 50 minutes or until thermometer reaches 160. If you're making one large loaf it will take longer.